JP3048953B2 - Non-aqueous electrolyte secondary battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte secondary battery, and more particularly to an improvement of a negative electrode thereof.

[0002]

2. Description of the Related Art Lithium (Li) and sodium (Na)
Non-aqueous electrolyte secondary batteries using an alkali metal such as an anode as a negative electrode have high electromotive force and are expected to have a higher energy density than conventional nickel cadmium storage batteries and lead storage batteries, and many studies have been made. In particular, many studies have been made on non-aqueous electrolyte secondary batteries using Li as a negative electrode. However, when a metal-like alkali metal is used for the negative electrode, dendrite is generated at the time of charging, a short circuit is easily caused, and the battery has low reliability. In order to solve this problem, use of an alloy negative electrode of Li as an alkali metal and aluminum (Al) or lead (Pb) has been studied. When these alloy negative electrodes are used, Li is occluded in the negative electrode alloy upon charging, and a highly reliable battery without dendrite generation is obtained. However, the discharge potential of the alloy negative electrode is about 0.5 V
Being noble, the voltage of the battery is also lower by 0.5 V, which also lowers the energy density of the battery. On the other hand, studies have been made using an intercalation compound of carbon and Li such as graphite as a negative electrode active material. Even in the case of this compound anode, Li does not enter the carbon layer and generate dendrites during charging. The discharge potential is about 0.1 V higher than that of metal Li, and the decrease in battery voltage is small. This can be said to be a more preferable negative electrode. However, this negative electrode active material also has a major problem. Li on charging
In the case of graphite, C ₆ Li is theoretically the highest value in the case of graphite, and the electric capacity in that case is 372 Ah / k
g. In addition, many proposals have been made for carbon having lower crystallinity than graphite as a material having a discharge capacity exceeding the above theoretical value.

[0003]

The discharge capacity of the above-mentioned carbon material is insufficient, and the capacity is greatly reduced with charge / discharge cycles. An object of the present invention is to provide a negative electrode that provides a nonaqueous electrolyte secondary battery that does not generate dendrite due to occlusion of Li during charging, has a large electric capacity, and has an excellent cycle life. In addition, the present invention provides a method for producing N
a can be occluded at a high capacity, and by using these negative electrodes, a highly reliable non-aqueous electrolyte secondary battery having higher energy density and excellent cycle life without short circuit due to dendrite is provided. The purpose is to:

[0004]

A nonaqueous electrolyte secondary battery according to the present invention comprises a positive electrode and a negative electrode having reversibility to charge and discharge,
And comprising a non-aqueous electrolyte containing alkali metal ions, specific to the negative electrode containing an alkali metal in a charged state
Characterized by containing a carbide of The alkali metal contained in the carbide is at least one of lithium and sodium. The negative electrode having the above configuration has a high capacity and a very excellent cycle life. By using this negative electrode, a non-aqueous electrolyte having a higher energy density, no short circuit due to dendrite, and a superior cycle life is provided. A secondary battery can be provided.

[0005]

DETAILED DESCRIPTION OF THE INVENTION The present invention is, as described above, is <br/> that the negative electrode contains certain carbides containing an alkali metal in a charged state. Here, the specific carbide is sodium
, Potassium, copper or manganese carbides. Specific examples of these carbides include Na ₂ C ₂ , K ₂ C ₂ , Cu ₂ C ₂ ,
Mn ₃ C, Mn ₂₃ C ₆ , Mn ₇ C ₃ and the like . Specific examples of addition, other <br/> _{carbide, Cr 4 C, VC 2,} Fe 2 C, FeC
And so on.

[0006]

[0007]

Embodiments of the present invention will be described below. Example 1 First, a test cell shown in FIG. 1 was made for Na ₂ C ₂ , K ₂ C ₂ , Cu ₂ C ₂ and VC ₂ in order to examine the characteristics as a negative electrode active material. Graphite was used in Comparative Examples. 10 g of each active material was mixed with 1 g of polyethylene powder as a binder to prepare a mixture. 0.1 g of this mixture was pressed into a disk having a diameter of 17.5 mm to form an electrode. FIG.
Shows a test cell using this electrode. The electrode 1 was arranged at the center of the case 2 and the microporous polypropylene separator 3 was arranged thereon. 1 mol / l lithium perchlorate (L
A mixed solution of ethylene carbonate and dimethoxyethane in which iClO ₄ ) was dissolved at a volume ratio of 1: 1 was poured on the separator as a non-aqueous electrolyte. On the other hand, the inside diameter is 17.5.
A sealing plate 6 was prepared, in which a metal Li4 having a thickness of 5 mm was attached and a gasket 5 made of polypropylene was attached to the outer periphery, and this was combined with the case 2 to form a test cell.

For each test cell, at a constant current of 2 mA,
Cathode polarization until the electrode becomes 0 V with respect to the Li counter electrode (equivalent to charging when the active material electrode is viewed as a negative electrode)
Then, anodic polarization (corresponding to discharge) was performed until the voltage of the electrode reached 1.0 V. The cathodic polarization and the anodic polarization were repeated to evaluate the electrode characteristics. Further, this charge / discharge was repeated up to 100 cycles, and the change in discharge capacity with the cycles was measured. Table 1 shows the initial discharge capacity and the ratio of the discharge capacity at the 100th cycle to the initial discharge capacity, that is, the discharge capacity maintenance ratio. The discharge capacity of the cell of this embodiment is extremely large. It was also found that the cell of the comparative example had a very large decrease in capacity due to the cycle, whereas the cell of the present example had almost no capacity decrease. After the cathode polarization at the 100th cycle of the test cell is completed,
When each test cell was disassembled, deposition of metallic Li was not observed in any case. As described above, in the electrode using the carbide of the present embodiment as an active material, Li is occluded in the electrode by cathodic polarization, Li occluded by anodic polarization is released, and no metal Li is deposited. Extremely large,
Excellent charge / discharge cycle characteristics.

[0009]

[Table 1]

[0010] In "Example 2" This embodiment, in order to examine the characteristics of the negative electrode active material for C r ₄ C, making the test cell shown in FIG. 1 in the same manner as in Example 1, the same as in Example 1 Tested under conditions. Table 2 shows the results. The discharge capacity of the cell of this embodiment is extremely large. In the cell of the comparative example, the capacity decrease accompanying the cycle was very large, whereas in the cell of the present example, it was found that there was almost no capacity decrease. After the cathodic polarization in the 100th cycle of the test cell was completed, the test cell was disassembled, and no deposition of metallic Li was observed in any case.
As described above, in the electrode using the carbide of the present example as an active material, Li was occluded in the electrode by cathodic polarization, Li occluded by anodic polarization was released, no metal Li was deposited, and the charge / discharge capacity was low. It is extremely large and has excellent charge / discharge cycle characteristics.

[0011]

[Table 2]

Embodiment 3 In this embodiment, Mn ₃ C, Mn ₂₃ C ₆ , Mn ₇ C ₃ , Fe ₂
In order to examine the characteristics of C and FeC as a negative electrode active material, a test cell shown in FIG. 1 was made in the same manner as in Example 1, and tested under the same conditions as in Example 1. Table 3 shows the results. The discharge capacity of the cell of this embodiment is extremely large.
In the cell of the comparative example, the capacity decrease accompanying the cycle was very large, whereas in the cell of the present example, it was found that there was almost no capacity decrease. After the cathodic polarization in the 100th cycle of the test cell was completed, the test cell was disassembled, and no deposition of metallic Li was observed in any case. As described above, in the electrode using the carbide of the present embodiment as an active material, Li is occluded in the electrode by the cathodic polarization, the occluded Li is released by the anodic polarization, and no metal Li is deposited.
The charge / discharge capacity is extremely large, and the charge / discharge cycle characteristics are also excellent.

[0013]

[Table 3]

Embodiment 4 In this embodiment, Na ₂ C ₂ , K ₂ C ₂ , Cu ₂ C ₂ and VC
_The cylindrical battery shown in FIG. 2 was constructed using the negative electrode containing ₂ as an active material, and the characteristics were examined. Natural graphite was used as the negative electrode active material of the comparative example. The battery was manufactured according to the following procedure. LiMn _1.8 Co _0.2 O ₄ as a positive electrode active material, mixing Li ₂ CO ₃ and Mn ₃ O ₄ and CoCO ₃ in a predetermined molar ratio, 90
It was synthesized by heating at 0 ° C. Furthermore, what classified this into 100 mesh or less was used as the positive electrode active material. 10 g of carbon powder as a conductive agent and 8 g of an aqueous dispersion of polytetrafluoroethylene as a binder and 8 g of pure water as a binder are added to 100 g of the positive electrode active material to form a paste, which is applied to a titanium core material. After drying and rolling, a positive electrode was obtained. The weight of the positive electrode active material of the positive electrode was 5 g. The negative electrode is
100 g of each of the above-mentioned carbide powders as an active material and polytetrafluoroethylene powder as a binder were mixed at a weight ratio of 100: 5, and the mixture was made into a paste using a petroleum-based solvent to form a copper core material. After the application, it was dried at 100 ° C. to obtain a negative electrode plate. Each of the negative electrodes had a carbide powder weight of 2 g.

The positive electrode plate 11 and the negative electrode plate 12 were spirally wound with a microporous polypropylene film of a separator 13 interposed therebetween. This electrode plate group is placed on top and bottom with insulating plates 16 and 17 made of polypropylene and inserted into a metal container 18 to form a step on the upper portion of the container 18. / L of lithium perchlorate dissolved in an isobaric mixed solution of ethylene carbonate and dimethoxyethane was injected, and sealed with a sealing plate 19 having a positive electrode terminal 20. The positive electrode lead 14 made of the same material as the core material connected to the positive electrode plate 11 is connected to the positive electrode terminal 20, and the negative electrode lead 15 made of the same material as the core material connected to the negative electrode plate 12 is connected to the battery case 18. I have. In this battery, the electric capacity of the positive electrode is larger, and the capacity of the battery is determined by the capacity of the negative electrode.

A charge / discharge cycle test was performed on the battery using each of these active materials as a negative electrode with a charge / discharge current of 0.5 mA / cm ² and a charge / discharge voltage range of 4.3 V to 3.0 V. Table 4 shows the initial capacity and the capacity retention rate after 100 cycles. The battery of this example has an extremely large electric capacity. Moreover, the cycle characteristics of the battery of this example are much better. After the charging of the 100th cycle was completed, the battery was disassembled and the presence or absence of metal Li was checked.
No Li deposition was observed in any of the batteries. Also,
Cr ₄ C, Mn ₃ C, Mn ₂₃ C ₆ , Mn ₇ C ₃ , Fe ₂ C and
Similarly, excellent results were obtained for FeC and FeC .

[0017]

[Table 4]

Embodiment 5 In the above embodiment, the alkali metal contained in the negative electrode during charging was Li, but in this embodiment, Na was studied. The cathode active material is NaNiO ₂ , and the non-aqueous electrolyte is 1 mol / l sodium perchlorate (NaCl
A cylindrical battery shown in FIG. 2 was constructed under the same conditions as in Example 4 except for the use of gamma-butyrolactone in which O ₄ ) was dissolved. In any of the batteries, the electric capacity of the positive electrode is larger, and the capacity of the battery is determined by the capacity of the negative electrode. Charge / discharge current 0.5mA / c for each battery
A charge cycle test was performed at m ² and a charge / discharge voltage range of 4.0 to 3.0 V. Table 5 shows the initial capacity and the capacity retention rate after 100 cycles.

[0019]

[Table 5]

The batteries according to the examples have an extremely large electric capacity as compared with the comparative examples, and also have excellent cycle characteristics.
After the charge at the 100th cycle was completed, the batteries were disassembled.
Was not observed. In addition, Cr ₄ C, Mn ₃ C,
Excellent results were similarly obtained for Mn ₂₃ C ₆ , Mn ₇ C ₃ , Fe ₂ C and FeC .

Further, in the above embodiment, the cylindrical battery has been described. However, the present invention is not limited to this structure, and the same applies to a secondary battery having a coin shape, a square shape, a flat shape or the like. The effect of is obtained.

[0022]

According to the present invention, by using a negative electrode having a high capacity and an extremely excellent cycle life, a highly reliable non-aqueous electrolyte secondary battery having a higher energy density and no short circuit due to dendrite can be obtained. Obtainable.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of a test cell for evaluating electrode characteristics of an active material of the present invention.

FIG. 2 is a longitudinal sectional view of a cylindrical battery according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electrode by this invention 2 Case 3 Separator 4 Metal Li5 Gasket 6 Sealing plate 11 Positive electrode plate 12 Negative electrode plate 13 Separator 14 Positive electrode lead 15 Negative electrode lead 16, 17 Insulating plate 18 Battery case 19 Sealing plate 20 Positive electrode terminal

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toyoguchi ▲ Yoshi ▼ Toku 1006 Ojidoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-4-237966 (JP, A) JP Hei 8-231273 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 4/02-4/04 H01M 4/36-4/62 H01M 10/40

Claims (4)

(57) [Claims] [Claim 1] comprising a positive electrode and the negative electrode, and a nonaqueous electrolyte containing alkali metal ions having reversibility with respect to charge and discharge, seen contains carbides said negative electrode containing an alkali metal in a charged state, the carbide Is sodium, potassium,
A non-aqueous electrolyte secondary battery comprising copper or manganese carbide . 2. A positive electrode and a negative electrode having reversibility to charge and discharge, and a non-aqueous electrolyte containing an alkali metal ion, wherein the negative electrode contains a carbide containing an alkali metal in a charged state, and the carbide contains Cr ₄ C, VC ₂ , Fe ₂
A non-aqueous electrolyte secondary battery comprising C or FeC . 3. The method according to claim 1, wherein the carbide is Na ₂ C ₂ , K ₂ C ₂ , Cu
₂ C _2, Mn ₃ C, a non-aqueous electrolyte secondary battery of claim 1, wherein the Mn ₂₃ C ₆ or Mn ₇ C _3. Wherein the alkali metal is a non-aqueous electrolyte secondary battery according to any one of claims 1 to 3, at least one of lithium and sodium.